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Green picture from Iscan Pro...

Discussion in 'Projectors, Screens & Video Processors' started by VintageMark, Jun 14, 2003.

  1. VintageMark

    VintageMark
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    Hi..

    Wondering if someone might be able to help...

    I have a Pioneer DV737 which I feed the component outputs from into an Iscan Pro and then onto my HT200 projector.

    The Iscan has a little switch which changes the output of the Iscan to either component or RGB (as I understand it).

    The problem is, if I set the output to component my projector displays everything as green, and only works if the switch is set to RGB.

    Anyone know why this might be?

    Many thanks.

    Mark.
     
  2. RichardA

    RichardA
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    Hi Mark,

    Uh, That's what the switch is supposed to do! it's switching the output from YUV component to RGB to suit the input on the display device - In your case it's an RGB input you are using so the picture is correct when the switch is set to RGB. If you had connected to a display with Component inputs the picture would look correct when set to component and very purple when set to RGB.

    The technical reason (if anyone is interested) for the green or purple is that a component signal has brightness (Y) voltage between 0V and +0.7 V but the colour difference signals (U and V, or R-Y, B-Y or Pr, Pb or Cr, Cb depending on who's in charge of labelling connectors!) are between -0.3V and +0.3V.

    For RGB the values of all three components is between 0V and +0.7V

    Therefore for any 'normal' picture the average voltages will have relatively high values for Y and very low values for U and V, while R,G and B will all have similar highish values.

    Generally, for a piece of equipment that uses one set of connectors for RGB and Component then it's common practice to use the same pin for Y and G and then Pb shares the B pin and Pr the R pin.

    So, if you have a Component signal going into an RGB input you'll get high Green and relatively low Red and Blue - leading to a Greenish image. And if you connect and RGB signal to a Component input you'll get high luminance (Brightness) with over voltage Pr and Pb which gives a Redish + Blueish tint which equals a purple tint.

    Hope this is of interest :lesson:
     
  3. VintageMark

    VintageMark
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    Hi Richard,

    Thanks for that... think I follow youre explanation! ;)

    So I guess my next question is....

    If I get a different cable... (one that goes from a 15pin VGA connector on the back of the Iscan to component cables at the other end) and plug this into the component in on my projector instead of the VGA input...

    Is the picture going to look much better than it does with the Iscan pumping out RGB? (Having changed the Iscan output to component of course!)

    Many thanks,

    Mark.
     
  4. RichardA

    RichardA
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    To be honest there is unlikely to be much difference between Component and RGB - certainly the theory is that, as the signal originates as Component on the DVD or whatever, and the display will always need to end up as RGB for the actual display device (whether it's the DMD chip, LCD panel, CRT tube or whatever), then it's siply down to where the conversion is best done.

    I have found that different displays can have different 'looks' with different inputs - for example a signal connecte to a 'VGA' input might be assumed to be always from a PC where it's more important to show clean, static graphics. While a Component input is more likely to be video and therefore tuned for moving images and better Black definition.

    At the end of the day, it does depend on the individual combination of equipment you have rather than an absolute rule, so feel free to try it and see!

    I've also just noticed your other post in the projectors section - trying the Component input as opposed to the VGA may clear the picture moving problem.

    Hope this helps!
     
  5. VintageMark

    VintageMark
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    Hi Richard...

    Many thanks for the extra info...

    Patience is not one of my strong points... I've already obtained and tried a component lead instead of the 15pin to 15pin lead...

    After quick first impressions... I would say the component does indeed look better... maybe down to that tuning you were talking about...

    However I did try it mostly due to my other problem... and it didnt solve that! :(

    Ah well... I guess Owl are about to make a small fortune out of me... again! :)

    M.
     

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